The present invention relates to image compression, and more particularly, to methods of efficiently reducing calculations during video signal compression.
With the development of mobile communications and satellite communications, wireless communication services have become more important in an information society. Multimedia wireless communication services are spread to provide wireless Internet access or video communications as well as transmission of voice or text information. Particularly, in the business of International Mobile Telecommunications-2000 (IMT-2000) and fourth-generation mobile communications using satellite digital multimedia broadcasting (DMB) systems, an environment enabling high picture quality moving pictures to be transmitted in real time has been built.
This technology has been commercialized due to the development of various image compression techniques by which an analog video signal is compressed and encoded into a digital signal and the digital signal is transmitted to and decoded by a receiver. Standardization of video signal coding has been led by a Moving Picture Experts Group (MPEG) under International Organization for Standardization/International Electro-technical Commission (ISO/IEC) and a Video Coding Experts Group (VCEG) under International Telecommunications Union Telecommunication Standardization sector (ITU-T). One of the latest video coding standards, H.264/Advanced Video Coding (AVC), was developed by a Joint Video Team (JVT) of ISO/IEC MPEG and ITU-T VCEG.
H.264/ACV introduces various techniques different from existing coding standards such as MPEG-2, MPEG-4, H.261, and H.263, thereby providing excellent compression capability. For instance, H.264/ACV codec performs motion estimation on a 4×4 block and can thus perform motion estimation on up to 16 4×4 blocks in a 16×16 macro block. As a result, H.264/ACV codec increases motion vector resolution to quarter-pixel precision, thereby enabling more precise motion estimation than existing codecs.
However, H.264/ACV codec calculates a residual signal between frames using multiple reference frames, thereby increasing the complexity of motion estimation compared to existing codecs. The increase of motion vector resolution also results in an increase in motion estimation complexity. The complexity of H.264/ACV makes it hard to adapt H.264/ACV to an application such as a real-time video encoder. Therefore, technology for efficiently reducing the complexity and maintaining high compression capability is desired. The above-described problems are not restricted to H.264/ACV but may be applied to compression techniques which will be adopted as standards.